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glibc  2.9
pthread_setcancelstate.c
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00001 /* Copyright (C) 2002, 2003 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <errno.h>
00021 #include "pthreadP.h"
00022 #include <atomic.h>
00023 
00024 
00025 int
00026 __pthread_setcancelstate (state, oldstate)
00027      int state;
00028      int *oldstate;
00029 {
00030   volatile struct pthread *self;
00031 
00032   if (state < PTHREAD_CANCEL_ENABLE || state > PTHREAD_CANCEL_DISABLE)
00033     return EINVAL;
00034 
00035   self = THREAD_SELF;
00036 
00037   int oldval = THREAD_GETMEM (self, cancelhandling);
00038   while (1)
00039     {
00040       int newval = (state == PTHREAD_CANCEL_DISABLE
00041                   ? oldval | CANCELSTATE_BITMASK
00042                   : oldval & ~CANCELSTATE_BITMASK);
00043 
00044       /* Store the old value.  */
00045       if (oldstate != NULL)
00046        *oldstate = ((oldval & CANCELSTATE_BITMASK)
00047                    ? PTHREAD_CANCEL_DISABLE : PTHREAD_CANCEL_ENABLE);
00048 
00049       /* Avoid doing unnecessary work.  The atomic operation can
00050         potentially be expensive if the memory has to be locked and
00051         remote cache lines have to be invalidated.  */
00052       if (oldval == newval)
00053        break;
00054 
00055       /* Update the cancel handling word.  This has to be done
00056         atomically since other bits could be modified as well.  */
00057       int curval = THREAD_ATOMIC_CMPXCHG_VAL (self, cancelhandling, newval,
00058                                          oldval);
00059       if (__builtin_expect (curval == oldval, 1))
00060        {
00061          if (CANCEL_ENABLED_AND_CANCELED_AND_ASYNCHRONOUS (newval))
00062            __do_cancel ();
00063 
00064          break;
00065        }
00066 
00067       /* Prepare for the next round.  */
00068       oldval = curval;
00069     }
00070 
00071   return 0;
00072 }
00073 strong_alias (__pthread_setcancelstate, pthread_setcancelstate)